1. Field of the Invention
This invention relates to a test strip for occult blood detection in excreta, comprising a chromogen, a hydroperoxide and, as a sensitizer, a thiazole compound. More particularly, the present invention is concerned with a test strip for occult blood detection in excreta such as urine or feces, comprising a chromogen, a hydroperoxide and, as a sensitizer, thiazole compound (I) of the formula: ##STR2## wherein R.sub.1 is an alkyl, a substituted or unsubstituted aralkenyl, or a substituted or unsubstituted aralkyl; R.sub.2 and R.sub.3 are each a hydrogen or an alkyl; and R.sub.2 and R.sub.3, when taken together with the adjacent carbon atoms, may form a benzene ring.
The test strip in accordance with the present invention can be used for the detection of occult blood in excreta (e.g. urine, feces), vomit, substances in the stomach, or spinal fluid. It is recognized that such hemorrhage is caused by cancer, ulcer, piles, typhus, scorbutus, purpura, renal insufficiency, bladder stones, kidney stones, and the like. Hemoglobin resulting from such diseases is usually in a very small quantity, and therefore cannot be examined with the eye unaided or through a microscope. According to the test strip of the invention, the occult blood can be easily and reliably detected with high sensitivity. Thus, the test strip of the invention is useful in early diagnosis of the diseases mentioned above.
2. Description of the Prior Art
The principle for the detection of occult blood is well known, i.e. hemoglobin in the blood catalyzes to decompose a hydroperoxide, and the liberated oxygen is transferred to a chromogen which is oxidized to give a colored substance, indicating the presence of occult blood. However, a test strip which is prepared by direct application of this principle does not give a satisfactory result in the detection of a very small amount of blood. Also, the test strip so prepared has a drawback in its insufficient stability during storage.
As a test strip including a sensitizer in addition to a chromogen for occult blood detection, there has hithertofore been known a test strip using quinine (Japanese Pat. No. 478,815) and a test strip using a phenanthridine (U.S. Pat. No. 3,853,472). However, the former does not have a sufficient sensitivity and the latter has a drawback that it contains a carcinogenic substance as a sensitizer. The sufficient sensitivity of the rapid test for occult blood is of decisive importance, and the safety in its handling must be considered. It is recognized in the art that in view of practical clinical application, sensitivity to detect blood with a concentration of more than 1:200,000 in dilution is required. Also, the physicians concerned have pointed out that excessive sensitivity in such test strip is not desirable, because a false positive color reaction may take place.
Apart from this prior art, a use of pyridine derivatives has recently been proposed in, for instance, U.S. Pat. No. 3,917,452. Although this proposal asserts that it can detect blood in the dilution of 1:1,000,000, it has not been commercially exploited and an accurate assessment of the actual advantages in enhancement of the sensitivity of diagnosis has therefore not been made yet.